If you know the instrument, use that.
If not, I use keyboard.
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Here’s an interesting tidbit…
The “keyboard” got its name because it was “just the keyboard”.
See, an organ has a keyboard. Piano has a keyboard. Even the harpsichord has a keyboard.
Most people say keyboard when they mean ‘The Synthesizer’. (which is also technically wrong, and let’s not get into the difference between synthesizers and digital pianos)
The ‘keyboard’ is the keys themselves, each individual key creates the keyboard. Much the same as each individual human makes the human race.
That is why all of those instruments have guys who are known as “Johnny on the keys”. They are all keyboard instruments.
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I would support a “general keyboard” option. But if we did that, I would want the non-general keyboard option removed and replaced with something else (I think we have electronic keyboard already)
Synthesizer is technically wrong, because the synthesizer got its name because of the way the sounds are made. They do not require a keys to operate them, but that would be the most common way.
They even sell keys (they fall under the blanket category of “midi controllers”). They are literally just a set of keys. You then plug them into whatever device you want to “control”. It doesn’t have to be a sound module, I set one up in a baseball field for the guy to control the graphics that get displayed on the jumbotron.